Light emitting diodes (LED) are widely applied in lighting, such as general lighting or automotive lighting, backlight module, and other fields. Generally, an LED planar light source module includes an outer frame where a reflecting film, a light guide plate, a diffusion plate, and a plurality of light reflecting films are arranged and stacked one by one. The LED light source is arranged on a side of the light guide plate. However, since the light guide plate is attached to the outer frame, lines of darkness are present in seams between the light guide plate and the outer frame, affecting the appearance. Moreover, due to the presence of the outer frame, such LED planar light source module is not capable of achieving a frameless appearance. Therefore a light source module without an outer frame is desired to achieve a frameless appearance.